You could always add a ‘System Exposed Parameter’ float and use it with float multiplies for particle scale, cylinder radius, and even velocity (anything really that it makes sense to scale with the effect). That way when you place the Niagara system you can just set the new parameter to what you need to change all the scales, or you can easily use that parameter in a blueprint, even dynamically if you want. It also means you can re-use the system at different scales for each instance in multiple places without having to create a new system (this applies to all parameters you may want to edit on a per actor instance basis).
If you’re not sure what I’m talking about let me know and I’ll take the time to explain how.